SITE INFORMATION AND CORRESPONDENCE

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510 E Magnolia -2 - 5 August 1998 Stockton On 1 August 1996, four 10,000-gallon, single walled steel USTs were removed from the site by Ramcon. One additional 10,000-gallon steel UST was removed on 23 October 1996. All five tanks stored diesel fuel for the boiler operations. At least 2 soil samples were collected beneath each UST, and 2 below the product piping. Detectable concentrations of TPHd,up to 7,600 mg/Kg,were detected in confirmation soil samples collected at the time of the tank removal activities. Based on the tank removal sampling results, SJCEHD required additional characterization activities be carried out at the site. On 10 July 1997, soil borings were advanced in the vicinity of the former diesel fuel USTs. At the time of drilling operations, SJCEHD field personnel observed no signs of soil impact. Analytical results from soil borings near the former diesel fuel UST, did not contain detectable concentrations of contamination above the laboratory reporting limits. Approximately 317 tons of diesel contaminated soil was removed, under manifest, from the Stockton Developmental Center on 22 January 1997. The soil was taken to Forward Landfill. Summary: Based on the information provided by SJCEHD, TPH contaminated soil remains in place below some of the former UST locations. Based on the confirmation soil sampling, the impacted soil does not appear to extend far below 15 feet bgs, and is not detected at 20 feet bgs. The vertical extent of soil contamination is adequately determined at this site. Confirmation soil sampling, and the subsequent soil boring information, indicates the horizontal extent of soil contamination has been adequately determined at this site. The greatest impact appears to be below the former 8,500-gallon tank that was closed in place. A mass balance calculation was performed and an estimated 100 to 150 cu. yds. of impacted soil remain in place below this tank. The soil appears to be confined to the immediate vicinity of the former tank, and based on soil sample results,does not extend to 20 feet bgs. Groundwater below the site is located at approximately 45 feet bgs. Groundwater is unlikely to be impacted by the remaining soil contamination. Based on the above information,the contamination at the site appears to pose little or no threat to water quality. Concurrence with the SJCEHD decision for no further action at the above referenced site is appropriate.